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Advanced Program Sample Lesson

Background and General Description of Lesson

Somes Sound is the only natural fjord on the East coast. It is a deep, narrow inlet of the sea carved into Mount Desert Island by a glacier. A ridge of material at the mouth of the sound restricts the free exchange of ocean and estuary water, creating a semi-closed system.

During this lesson, students collect chemical, physical and biological data within Somes Sound. The goal is to assess the fjord’s ecological health and ability to sustain life. Traveling by boat, students and instructors run tests at 3-4 different areas in the Sound and interpret the data collected.

Test 1: Water Collection

To run our chemistry tests, we need water from the top and the bottom at each station. This student is sending a bottom water sampler 40 feet down in order to conduct a series of chemical tests.

Test 2: Current Speed

Discovering the speed of the water’s movement helps us understand the dissolved oxygen and temperature readings. This student is timing how long it takes the paddle drogue to travel a set distance. He then puts this data into an equation to figure out the current’s speed at that station.

Test 3: Salinity

The salinity of the water will change as we move up the Sound and closer to the freshwater source. This student has just used a hydrometer to measure the density and temperature of the water. She is working with staff member Liz Pesce to chart salinity. Because salt water is denser than fresh water, it tends to sink to the bottom. But if the freshwater is much colder than the saltwater, then the freshwater will be denser and sink to the bottom. Variations in salinity influence the types of organisms found.

Test 4: pH

This student is using a color comparator to determine the pH of the water. PH is a measure of the acidity or alkalinity of a solution. The pH scale is 1 (acidic) to 14 (base) with 7 being neutral. Oceans tend to be base, running in the low 8’s. This is mostly due to the presence of certain dissolved substances such as carbonates. In areas where there are a large number of animals releasing carbon dioxide (CO2) and not enough algae to take it in (they use CO2 for photosynthesis), the water will become more acidic. As humans create more CO2 through the burning of fossil fuels, and as deforestation limits the number of land plants that can help store CO2, the oceans are under increasing pressure to absorb the problem. Long term it may make the oceans more acidic and harm marine organisms that can’t handle the change.

Test 5: Dissolved Carbon Dioxide & Dissolved Oxygen

These students are testing for the levels of dissolved carbon dioxide (CO2) and dissolved oxygen (DO2) in the top and the bottom water samples. The phytoplankton and algae release oxygen as a by-product of photosynthesis while carbon dioxide is a by-product of respiration and is released by animals into the water. Water movement (such as strong currents, wave action, wind and even boats) can also add oxygen to the water. Though our surface atmosphere is about 21% oxygen, we measure the ocean’s oxygen in parts per million because there is so little retained in the seawater. A great deal of the ocean’s oxygen is released into the atmosphere.